In a long term evolution (LTE) system, in a release (R) 8/9/10/11, all LTE carriers are backward compatible, and a primary synchronization signal (PSS), a secondary synchronization signal (SSS), a physical broadcast channel (PBCH), a system information block (SIB), a physical downlink control channel (PDCCH), cell-specific reference signals (CRSs) of all frequency bands and all subframes, and the like, that have a same resource location and a same sending manner as those in an LTE system of R8, should be sent on each carrier. In an LTE R8/9 release, demodulation of a physical downlink shared channel (PDSCH) is based on only a CRS. In an LTE R10 release, a demodulation reference signal (DMRS) is further introduced and is also used for PDSCH data demodulation, and the DMRS is sent only on a physical resource block (PRB) that is used to transmit a PDSCH. Further, in an LTE R11 release, an enhanced physical downlink control channel (EPDCCH) is further introduced, the EPDCCH and a PDSCH are frequency division multiplexing, and demodulation of the EPDCCH is based on a DMRS.
In an LTE R8/9/10/11 release, a maximum system bandwidth that can be supported by a carrier is 20 MHz, and an LTE terminal can receive and send data on an entire carrier. In a later LTE release, low-cost machine type communication (MTC) user equipment (UE) is introduced, and this type of user equipment can receive and send data only in a relatively low bandwidth (that is, a narrowband), so that a downlink data processing capability and data storage capability that are of an MTC terminal are lowered and costs are reduced.
In an LTE R12 release and a later release, a new carrier type (NCT) is introduced. On an NCT carrier, a single-antenna CRS is sent only in a small quantity of subframes, and the CRS is not used for PDSCH demodulation. In a release later than an LTE R11 release, a new carrier type carrier is used to serve LTE terminals that have different capabilities, and serve multiple types of services such as unicast and an multimedia broadcast multicast service (MBMS). One of design objectives for the new carrier type is highly efficient spectrum utilization, and therefore, how to design a transmission mechanism of a common control channel on an NCT carrier to obtain relatively high spectrum utilization is a problem that needs to be resolved.